Electrical pulse slicing circuit



Nov. 4, 195a R. c. [MM 2,859,344

ELECTRICAL PULSE SIC-ICING CIRCUIT Original Filed June 4, 1952 l'i oRueYSi United States Patent Ofi ice 2,859,344 Patented Nov. 4, 1958 ELECTRICAL PULSE SLICING CIRCUIT Ronald Charles 1mm, Ruislip Manor, England, assignor to The General Electric Company Limited, London, England Original application June 4, 1952, Serial No. 291,765, now Patent No. 2,802,102, dated August 6, 1957.

Divided and this application March 20, 1957, Serial No. 647,309

Claims. (Cl. 250-27) The present invention relates to electrical pulse slicing arrangements.

In signalling systems which utilise pulse code modulation, the waveform of the transmitted signal may sutfer appreciable distortion during transmission, for example due to the addition of noise. Thus in a system using binary coding in which intelligence is transmitted by a signal having either one or two levels, which may be pulse and no pulse respectively, this noise will appear as modulation on both these levels. In order to separate the required pulse signal from the noise at the receiving terminal of the system, it is known to reshape the pulse signal by effecting pulse slicing at a level between the two levels of the pulse code signal itself, this slicing level being chosen so that it is not crossed by peaks of the noise modulation on either of the levels of the pulse signal or at least so that the number of noise peaks which cross the slicing level is a minimum.

It is desirable that slicing shall be efiected at substantially a predetermined level relative to both the levels of the pulse code signal but it will be appreciated that if the pulse code signal is supplied to the slicer through a valve amplifier, for example,'the absolute value of these two levels may vary. The direct current component of the pulse code signal may be restored before slicing by means of a known clamping circuit but this is not entirely satisfactory since it merely ensures that the slicing level has a predetermined difference from one or other of the levels of the pulse code signal and does not take into account variations in the difference between those two levels.

It is one object of the present invention to provide a pulse slicing arrangement in which this difliculty is overcome.

According to the present invention, an electrical pulse slicing arrangement comprises a voltage slicer, an input path over which is supplied to the voltage slicer a pulse signal to be sliced, first means which is connected to the input path and which supplies a first unidirectional voltage that is a measure of the most positive level of the pulse signal, second means which is connected to the input path and which supplies a second unidirectional voltage that is a measure of the most negative level of the pulse signal, a potential dividing network connected between the first and second means so that one endof the network is 'maintained at the said firstunidirectional voltage and the other end is maintained at the said second unidirectional voltage, said potential dividing network having a tapping point, and a connection between the voltage slicer and the said tapping point to maintain said tapping point at a voltage equal to the level at which the voltage slicer operates so that the most positive and most negative levels of the pulse signal supplied to the voltage slicer lie on opposite sides of the said slicing level.

In one arrangement, there are two parallel-connected paths each consisting of a rectifier element and a capacity connected in series, with unlike poles of the two elements connected together and one side of each of the two capacities connected together while the pulse signal to be sliced is arranged to be supplied through a further capacity one side of which is connected to the junction of the two rectifier elements. The potential dividing network is connected between the junctions of the said rectifier element and the said capacities in each of the two paths. The voltage slicer is arranged to slice the signal at the junction of the two rectifier elements while the tapping point on the potential dividing network is maintained at a predetermined voltage.

A pulse slicing arrangement in accordance with the present invention for reshaping pulse code signals will now be described by way of example with reference to the accompanying drawing which shows the circuit of the arragement. This arrangement is for reshaping a pulse code signal of the two-level binary type.

Referring to the accompanying drawing, the pulse code signal which is to be sliced is supplied through a condenser 1 between the grid 2 and the cathode 3 of a pentode thermionic valve 4 'whichis arranged to operate as a conventional amplifier. The signal developed across the anode load resistor 5 of this valve is supplied to a network 6 for determining the level at which slicing is to be effected. This network 6 is formed by two parallel-. connected paths 7 and 8 each of which consists of a condenser 9 or 10 and a diode thermionic valve 12 or 13 connected in series. One side of each of the two condensers 9 and 10 is connected to earth while the other sides of these two condensers are connected to the anode 15 and cathode 16 respectively of the two diode valves 12 and 13, the remaining two electrodes 17 and 18 of the diode valves 12" and 13 being connected together. A condenser 20 is connected between the anode 14 of the pentode valve 4 and the junction of the electrodes 17 and 18 of the diode valves 12 and 13. Resistors 21 and 22 having the same resistance are connected in seriesbetween the junctions of the condensers 9 and 10 and the diode valves 12 and 13 in the two paths 7 and 8.

A double triode valve 24 is arranged as a voltage slicer and has a resistor 26 connected between its cathode 25 and earth. A connection 30 is provided between the junction of the electrodes 17 and 18 of the diode valves 12 and 13 and a control grid 23 of the double triode valve 24 while both the junction of the two resistors 21 and 22 and the other control grid 32015 the valve 24 are connected to a positive supply line 19. The anode 27 of the valve 24 that is associated with the grid 23 is connected directly to a positive supply line 28 so as, to be maintained at approximately 250 volts above earth while a resistor 29 is connected between that supply line 28 and the other anode 31. The output from the slicer is taken from across the resistor 29 through a condenser 33. i V V 4 Considering now the operation of the arrangement described above, itwill be appreciated that the pulse signal to be sliced is fed through the pentode valve 4 and the condenser 20 to the control grid 23 of the valve24 which constitutes the voltage slicer, the level at which slicing is efiected being determined by the steady voltage on the control grid 32. The condenser 9 and diode valve 12 act after the manner of a peak volt meter'so that there is developed across the condenser 9 a voltage equal to the m'ostnegative level of the 'pulse code signal supplied to the control g'rid23. Similarly there isde-' veloped across the condenser 10 a voltage equal to the most positive level of the pulse signal. 'In other words the ends of the potentiometer formed by the resistors 21 and 22 are maintained at unidirectional voltages equal to the most positive and most negative levels of the pulse code signal supplied to the control grid 23. It follows that the most positive and most negative levels of the V t pulse signal supplied over the connection 3040,

age'slicer formedbvthe valve 24 lie one on either side 'ofthesliciuglevel.

In the arrangement being described the input pulse code sign l is madeup .of aplurality. of pulse intervals 'whiehieach lasts'for' znimieroseconds and'in each'iof jjv vhicntneremayorma nothei'a puls dependin npen "the intelligence being transmitted. If 'tWQf'or more a djacent pnlse'intetvals"eachcontain afpulse 'thereis" thus produced, in efiect, a"s'ingle pulse offincrease'fduration. In order to prevent any. appreciable'variatiod'inf'the unidirectional voltages "developed across the condensers 9 "andilo when either "a plurality of adjacent pulse 'intervals have no pulse or'alternatively, each contain a pulse,.it is necessary for the combinationoffthe con- 'densers '9: and"1'0j'andj' the"resistors"21fand' 22 to have al'hig'h time constant. ""Ihus each'ofth'ese condensers 9 and .10 mayfhave, a'capacity of fOl 'microfarad and each of the resistors 21 "and i 22 a resistance! of "100,0001ohms so that the' said time constantfis one'inillis'econd, which is large comparedwith the'dura'tion of each individual pulse interval. 7 I

"The arrangement'descr'ibed above for slicing a' twolevel signal'may be. extended to slicing a three-level signal. Inthis' case it is necessary to effect slicing at'two 'difiere'nt'slicing'levels forthis purpose'there are provided" two' double triode valves similar to the valve 24. 'Each "ofthese'doubledriode valves 'has'an associated'resistor 'connectedbetweenits cathode and earth while thetwo trio'de portions corresponding to the right hand portion of the' 'valve 24 in the accompanyingidrawinghave a common load resistor across whichlis developed the output signal. Both the 'voltage slicers are supplied with the same pulse signal in the manner previously describedand the junction of the resistors21 and 22 is connected to the positive supply'line 19. For the purpose of controllingthe slicing levels at-which the two slicers operate, the appropriate control grids, corresponding to'the control grid '32, of the two double triodes are connected'totapping points on the resistors 21 and 22 respectively. 'This invention is 'adivision,of my application Serial No. 291,765, 'filed 'June 4, l952,'for Electrical Pulse Slicing Circuit whichhas issued as U. S. Patent No. 2,802,102, dated August 6, l957,'the said patent. claiming apriority date of June 8, 1951, in accordance with the requirements of title 35 U. S. Code, sec. 119.

I claim: 1. An electrical. pulse slicing arrangement comprising a voltage slicer, an input path over which is suppliedlo thevolt-age slicer: a pulsesignalto be sliced, first means which is connected to the input path andwhichsupplies a first nnidirectionalvoltage that is a measure of-the most positive level of the pulse signal, second-means which is connected to the input path and which supplies a second unidirectional voltagethat is'a measure-of the most negative level of the pulse signal, a potential divide ing. network connected between the first and-second rmeans so: thatoneend of the: network is maintained ate-the esaid first unidirectional voltage -andthefother end s-is maintainedat the said second unidirectional voltage, Jsaid: potential dividing network having-a tappingipjoint; and' a connection ---between' the voltage, sheer and 1 the saidslt'apping point to-maintain sa'id tapping point tat'avoltage equal torthe-level at, whichxthevoltage :slicer operates so that the most-positive and most negative levels-" of the; pulse signal supplied to the'voltageslicerlie on-o'pposite sidesof-ethessaid slicing level.

2 An electrical pulse slicing arrangement according to "claim 1 wherein the resistances bfthe two partsofthe nected-in a common supply circuit, a-resistance"in"said commonsupply circuit for the cathodes,'the"control2 g1id of the first valve being connected to the inpufp' h the control grid of the second valvebeinguphysically on-, nected to the tapping point on the potentiaPdividi-ngmetwork, means maintaining thecontrol gridof the second valve at a predetermined voltage, a resistanceco'niiected in the anode circuit of the second valve, and an output path connected between said last-named resistance and the anode of the second valve. I f

4. An electrical pulse slicing 'arrang'ement'comprising a pair of parallel-connectedpaths each consistingofa rectifier element and a capacity connected in series with unlike poles of the two rectifier elements c0nnected'-to-' gether and one side of each of the two capacities 'connected together, an input path over which a pulse to be sliced is supplied to the parallel-connected: paths and which contains a capacity one sidejof which is"'c"onnected to the junction of the two rectifier 'elements,a potential dividing network connected between'thejunctions of the saidrectifier'elements and the said capacities of each of the two paths, aivoltage slicer, a connection'for supplying to the'voltage =slicer the'pulsesignal developed at-the junction of the tworectifien elements, means to maintain a-tappingpoint on the said'potential' dividing network at a '-predetermined 'voltage, and a' connection between the voltageslicer and a tapping point 'onthe'js'aid potentiah dividing network over which'issupplie'd to the voltage slicer a' potential which controls the level afwhich it operates, this lever at which the voltage's'licer operates being between the most positive and most negativelevels of the pulse signal supplied thereto. I

5. An electrical pulse slicing arrange'ment"comprising a pair of parallel-connected paths each consisting 6m rectifier' elernent and a capacity connected"in'-'series with unlike -poles=ofthe two 'r'ectifier elements connectdi'together and one side of each of the tWo capacitiesco nfnected together, an input path over whicha pulse signal tobe sliced is supplied to the-parallel-connected fifths and which contains a capacity one s'ide of'whichfi nected to the junction of the two rectifier element "'a potential dividing network-connected betweenthe ju'nctions of the said rectifier elements and the said'capa'citie s of each of the two paths, a voltage slicer to effect slicing of the signal supplied thereto at 'a pred'etenninedslic'ing voltage, means to maintaina tappingpoint-onthe said potential dividing network at the-said predetermined voltage, and a connection for supplying tothe voltage slice'r the I pulse signal developed at the junctionof-the two vrectifier elements.

References Cited in the file ofthis patent FOREIGN PATENTS Australia Mar. 15, *1954 

